In a Device to Device (D2D) communication system, when a service which needs to be transmitted exists between User Equipment (UEs), service data between the UEs are not forwarded by a base station but are directly transmitted to a target UE by a data source UE through an air interface. FIG. 1 illustrates a schematic diagram of a D2D communication structure according to the related art. As illustrated in FIG. 1, this communication mode has features which are obviously different from the features of the communication mode of the traditional cellular system. For near-distance communication users who can apply the D2D communication mode, D2D transmission not only can save radio spectrum resources, but also can reduce the data transmission pressure of a core network, and can reduce the occupied system resources, increase the spectrum efficiency of the cellular communication system, reduce the transmitting power consumption of the terminal and reduce the network operating cost to a very great extent.
In the traditional cellular communication system, radio resources of UE are uniformly controlled and scheduled by an evolved NodeB (eNB), the eNB indicates downlink or uplink resources configured by the UE through a Physical Downlink Control Channel (PDCCH), and the UE indicates to receive data signals transmitted by the eNB on corresponding downlink resources or transmit signals to the eNB on uplink resources according to the configuration by the eNB.
In a Long Term Evolution (LTE) system, radio resources are divided in a time domain by using radio frame as a unit, and each radio frame is 10 ms and includes 10 subframes. Each subframe is 1 ms and is divided into 2 slots which are respectively 0.5 ms, as illustrated in FIG. 2. When a system frame structure adopts a Normal Cyclic Prefix (Normal CP), each subframe includes 14 Single-carrier Frequency Division Multiple Access (SC-FDMA) symbols or Orthogonal Frequency Division Multiplexing (OFDM) symbols, and is divided into 2 slots, herein each slot includes 7 symbols. When the system frame structure adopts an Extended Cyclic Prefix (Extended CP), each subframe includes 12 symbols and each slot includes 6 symbols. In a frequency domain, resources are divided by using subcarrier as a unit. Each subcarrier includes 15 kHz or 7.5 kHz resources.
According to the division unit of the time domain and frequency domain resources, the eNB schedules the minimum unit of time and frequency resources as a Resource Block (RB) for the UE, the RB is defined as 1 slot on the time domain and continuous NscRB subcarriers on the frequency domain, NscRB=12, 24, as illustrated in FIG. 3, the eNB specifically has two modes for resource allocation indication of the UE, i.e., a resource allocation indication type 0 and a resource allocation indication type 1, and based on the two resource allocation indication types, the eNB can flexibly schedule and indicate one or more RB resources for the UE.
In cellular communication, the eNB schedules and indicates Physical Downlink Shared Channel (PDSCH) resources configured at current subframes to the UE on PDCCH resources of downlink subframes # n, and the UE receives the indication information in the PDCCH, receives signals on corresponding RBs in the subframes # n according to the indication information and obtains data transmitted by the eNB, as illustrated in FIG. 4. Therefore, in D2D communication, when the transmitting UE indicates the used D2D data channel resources to the receiving UE, the method for the eNB to schedule and indicate the resources to the UE in the cellular communication cannot be used.
Aiming at the problem that the transmitting UE for D2D communication in the related art cannot indicate the used D2D data channel resource, no effective solution has been put forward.